The present invention relates to a novel copolymer and applications thereof and more specifically the present invention pertains to a copolymer of methacrylic acid with ethylene glycol dimethacrylate; a method for the preparation thereof; an adsorbent or a concentrating medium containing the same; a loop of an injector for chromatography packed with the adsorbent or concentrating medium; a needle for solid phase micro-extraction (SPME) packed with the adsorbent or concentrating medium; a kit containing the needle and used for the preparation of a sample for analysis; and a method for concentrating a sample and a method for analyzing an analyte present in the sample, which make use of the kit.
The solid phase microextraction (hereunder referred to as “SPME” or “solid phase extraction”) is a most powerful or effective tool for the preliminary concentration of a sample, which is inspected for the presence of an organic compound to be analyzed, such as an aqueous sample analyzed according to the gas chromatography (GC) technique. The SPME technique may simply be handled and requires the use of a small amount of a solvent consumed, as compared with the conventional solvent extraction technique and therefore, there have been presented or proposed a large number of applications of the SPME/GC technique. When dipping an SPME fused silica rod in the sample solution, the analyte is extracted into the polymer film on the surface of the silica rod. Then the fused silica rod is introduced into the sample-injection port of a gas chromatograph and a heat is then applied thereto so that the analyte molecules undergo desorption by the action of the heat. In contrast with the foregoing succeeded example, there have been known only a small number of reports concerning the combination of the SPME technique with the liquid chromatography (LC) technique or the electrophoretic separation technique for the analysis of a non-volatile compound. This is because, the mechanism of the on-line interface is complicated and the operations for desorption are quite difficult.
Recently, there has been developed another SPME technique or an in-tube SPME technique in which the LC separation device is directly connected to the SPME device without using any interface. In this method, the extraction medium used is an open tubular GC hollow capillary column. If a sample solution is passed through the column using a microflow pump, an analyte present in the aqueous sample solution is extracted into a polymer film applied onto the inner wall of the hollow capillary. A small amount of an organic solvent can likewise be passed through the hollow capillary to thus desorb the analyte thus extracted. This method does not require the use of any desorption device for feeding the extracted solute into the separation device and therefore, any process requiring difficult operations can be eliminated and the amount of the organic solvent required for the desorption can be reduced to a level as low as possible.
The inventors of this invention have already tried to adopt a wire-in-tube structure as a hollow capillary for extraction used in the analysis of a tricyclic antidepressant present in the human urine. In this wire-in-tube structure, the inner volume of the hollow capillary for extraction can substantially be reduced by the insertion of a stainless wire into the hollow capillary, while maintaining the surface area, which comes in contact with a sample solution. Such a construction would permit the further improvement of the concentration effect as compared with that achieved by the conventional in-tube SPME technique. Moreover, this fact suggests that the on-line wire-in-tube SPME/LC device would enable the high-speed analysis of a variety of organic compounds present in biological and environmental sample matrices.
On the other hand, the analysis of phthalic acid esters present in aqueous sample matrices in low concentrations have been considered as one of most important problems to be solved because of the estrogen actions of the compounds. There have widely been investigated techniques for the quantitative analysis of phthalic acid esters as internal secretion-disturbing substances and for elucidating the functions thereof, but there has still been desired for the development of an effective and rapid extraction-concentration technique, which never requires the use of a large amount of a solvent, in the practical analysis of environmental aqueous samples.
Further, there has been proposed a technique, which makes use of polymers derived from divinyl benzene as a medium used in the absorption-desorption of the foregoing samples to be analyzed. However, only specific samples are adsorbed on such polymers and, in particular, these polymers suffer from various problems. For instance, they cannot adsorb any alcohol, it is difficult to use them since the particle size thereof is too small and they are quite susceptible to water vapor. For this reason, there has been desired for the development of an absorption-desorption medium usable for various purposes.